In countries where they are found, the P2Mk2 and the P4Mk1 are often refered to as the P4Mk1 and P4Mk2. I will follow that convention here.

The
P4Mk1&2 are round plastic-cased anti-personnel blast mine. With a very low metal content, these mines are difficult to detect with many metal detectors. The picture below shows the metal content (the twisted length of thin shear-wire shown in the clear plastic inside the top of the mine should be included).

Manufactured in Pakistan, they have been found in Afghanistan, Angola, Eritrea, Ethiopia, Pakistan, Somalia, India and
Sri Lanka.
The mine casings are usually brown or green, with a yellow ring between the top and bottom halves. Arming caps are reported to be white, and screw over the entire top of the mine. They can be replaced to effectively neutralise a mine after arming. In Sri Lanka, most mines are disarmed by unscrewing the base of the mine, so removing the detonator and booster. When enough pressure is applied to the circular pressure plate on top of the mine, the shear-wire is broken releasing the sprung firing pin into the friction sensitive detonator. The mines are used as the initiators of several of Pakistan's Anti-Tank mines.

Height:
40mm
Diameter: 70mm
Main charge: 30g Tetryl

The picture shows two P4Mk2 mines. In the foreground is the baseplate with the booster/detonator assembly, and a separated detonator. The pressure plate of the mine on the left is depressed, showing that it has functioned without detonating. This has occurred in many (more than 50% of those I have personally seen) of the P4 mines recovered in Sri Lanka (and which were later disarmed by unscrewing the baseplate). When the baseplate is unscrewed the detonator is visible and frequently shows the hole made by the firing pin entering it. This can be seen in the picture below.

Pakistan is not a signatory of the Ottawa Convention banning the sale and transfer of anti-personnel blast mines. Since 1997, these mines (and all other minimum metal designs) should have been supplied with "detection rings" (washers) to aid metal-detection.